The present invention relates to electronically controlled pressure systems. It finds particular application in conjunction with solenoids used for controlling pressure in pneumatically operated vehicles systems and will be described with particular reference thereto. It will be appreciated, however, that the invention is also amenable to other applications.
Solenoids are commonly used in vehicle compressed air systems for controlling flow of the compressed air from a supply air reservoir to a vehicle sub-system (e.g., a braking system) operated by the compressed air. It is not uncommon that the vehicle sub-system achieves optimal operation when the pressure of the compressed air within the vehicle sub-system is within a target range. Therefore, a solenoid is typically used in conjunction with a separate pressure limiting valve to more precisely control the amount of compressed air supplied to the vehicle sub-system.
When the pressure in the vehicle system drops below a cut-in pressure, the solenoid supplies the compressed air from the supply air reservoir to the vehicle sub-system via the pressure limiting valve. Once the pressure within the vehicle sub-system reaches a cut-out pressure, the solenoid is, for example, deenergized to prevent additional compressed air from being supplied to the vehicle sub-system. Although the cut-out pressure is designed to ensure the pressure within the vehicle sub-system is within the target range, the actual pressure supplied to the vehicle sub-system by the solenoid may overshoot the target range. In this case, the pressure limiting valve acts to exhaust any excess pressure from the vehicle air sub-system until the pressure of the compressed air within the vehicle sub-system is within the target range.
The present invention provides a new and improved apparatus and method which addresses the above-referenced problems.